Devices designed for the at least partially automated sterilization of medical instruments are known in the art.
For example, the Steris One system, available from Steris Corporation of Mentor, Ohio, functions by first positioning the contaminated instrument in a chamber within the machine and attaching tubing to the fluid channels of the instrument chamber. A dose of the antimicrobial composition is inserted into the machine. An aspirator is then inserted into the top of the package that contains the antimicrobial and the lid of the machine is closed. A technician starts a cycle and a cycle consists of four stages: (1) the system plumbing is rinsed; (2) the entire interior of the machine fills with water and a circulation pump mixes the antimicrobial chemicals into the water, producing, in situ, the antimicrobial solution, and the machine heats the antimicrobial solution to a desired temperature; (3) once the antimicrobial solution reaches the desired temperature, it is circulated through the system at that temperature for a specified length of time; (4) the antimicrobial is rinsed out of the system with sterile water and the cycle is complete. The technician opens the lid and removes the sterilized, but wet instruments for immediate use.
Antimicrobial or antimicrobial solutions adapted for use in such sterilizing devices are also known, but each suffers drawbacks either in terms of storage, handling, and corrosiveness, or compromised capability of rapid in situ dissolution of the composition components. Typically, known antimicrobial systems rely on peracetic acid or other strong oxidants as the sterilizing agent.
Peracetic acid is an unstable compound prone to decomposition into acetic acid and hydrogen peroxide, which upon further decomposition produces oxygen gas. The decomposition products have minimal biocidal activity as compared to peracetic acid. In order to minimize the decomposition rate and improve its shelf life, manufacturers of peracetic acid typically add about 1% sulfuric acid to the peracetic acid. This increases corrosiveness of the antimicrobial and necessitates the addition of extra buffers and corrosion inhibitors. In addition, containers for peracetic acid must be vented to permit escape of the oxygen gas and prevent a problematic rise in pressure. In addition to the vents allowing the escape of the oxygen gas, the vents also allow for the escape of the concentrated peracetic acid vapors, which are noxious, explosive, and potentially harmful. Storage conditions which may subject the peracetic acid container to increases in temperature must be avoided, and storage of containers which vent materials into the atmosphere is problematic and subject to additional regulatory intervention.
U.S. Pat. No. 5,077,008 to Kralovic et al. discloses an antimicrobial solution comprising, inter alia, a strong oxidant selected from organic peroxides, peracids, chloride releasing compounds, chlorine dioxide, hyperchlorides and phenol, and a particular anti-corrosive system. Peracetic acid or combinations of peracetic acid with other oxidants are disclosed as preferred oxidant components. This patent teaches a specific, synergistic corrosion inhibiting system that comprises at least two specific corrosion inhibitors, one of which is preferably a phosphate, but between phosphates, molybdates and triazoles. Other components include buffering agents, sequestering agents, and wetting agents. However, this antimicrobial delivery system is subject to the known disadvantages of using reactive liquid reagents.
U.S. Pat. No. 5,037,623 to Schneider et al. discloses ampule-based systems for maintaining reactive components and reagents separately until immediately prior to use. Schneider teaches use of a vented, liquid-containing ampule which may be disposed in any orientation without leaking liquid. The preferred antimicrobial is peracetic acid. The vent insures that the pressure within the ampule does not become so great that it ruptures during storage and/or handling. The vent is situated on the ampule such that liquid does not leak from the vent aperture regardless of the orientation of the ampule. However, storage of ampules which continually vent poses additional challenges, and the oxidant in this system is still subject to continual degradation which may be enhanced by environment conditions.
Other systems have been designed to circumvent the disadvantages to vented liquid ampules which rely on powdered ingredients to the antimicrobial composition. For example, U.S. Pat. No. 5,116,575 to Badertscher teaches a dry composition of powdered ingredients, including a powdered borate and a powdered water soluble acid precursor, along with the use of dry reagents, including an acetylsalicylic acid precursor and a sodium perborate peroxide source, and steps requiring the utilization of powdered acetylsalicylic acid and a powdered perborate. Badertscher also discloses a sterilization apparatus including a receiving station for receiving the dry ingredients and a disposable ampule-based delivery, but requires that the ingredients which form the oxidant component be sealed in the ampule in powdered form. Here, the strong oxidant is delivered via a powdered precursor. However, there are drawbacks to the utilization of powdered ingredients intended for in situ dissolution. The amount of time required for effective dissolution of solid ingredients into a water solvent is greater and less consistent than that for liquid ingredients.
The dry reagent receiving region is connected to a water supply which selectively flows through and dissolves the dry reagents in the reagent receiving region forming the microorganism killing oxidant solution. All the ingredients which dissolve to form the oxidant solution are present in the reagent receiving region. The ampules supply a premeasured dose of powdered reagents. In system designs wherein flowing water is relied on to dissolve dry ingredients, concentrations of components in the resulting antimicrobial solution will vary over time according to solubility.
Hence, there is a need in the art for antimicrobial systems which overcome these and other disadvantages.